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Geology of the Cerro Negro Norte Fe-Oxide (Cu-Au) District, Coastal Cordillera, northern ChileRaab, Alexander K. 27 August 2001 (has links)
The intrusion-related Cerro Negro Norte Fe-oxide (Cu-Au) deposit is hosted in andesites and diorites of the early to middle Cretaceous Coastal Cordilleran arc of northern Chile. Tabular and irregularly shaped magnetite orebodies are localized on splays and fractures of the regional NINE striking Atacama Fault Zone. Production from this district was [approximately]100 MT @ [approximately] 65 wt. % Fe. Early Na-Ca alteration assemblages associated with magnetite �� apatite �� pyrite �� chalcopyrite ore include actinolite, marialitic scapolite, oligoclase, titanite, and epidote. Na-Ca alteration is extensive (>4 km�� in area), locally pervasive in the district, and is locally associated with granodiorite dike emplacement. The alkali-rich alteration and sulfide poor mineralization at CNN is characterized by metasomatic exchange of major, minor, and trace elements (added Fe, Na, Ca, Cl, P, Rare Earth Elements) between andesitic and diorite host rocks and halite-saturated saline hydrothermal fluids preserved as inclusions. Intrusion-heated fluids converge along the Atacama Fault Zone, and dikes, and may have been derived either from seawater or evaporitic water trapped in sedimentary rocks of the protoarc. Younger, cross-cutting hydrothermal assemblages such as tourmaline-quartzsericite (�� breccias), associated with granodiorite dikes, and chiorite-calcite-tourmalinequartz assemblages are related to pyrite �� chalcopyrite �� hematite and Cu-Au mineralization. Supergene minerals include goethite, Cu-carbonates and Cu-oxide. Later carbonate (dolomite) alteration is also localized along northeast-striking faults. Inferred Cu-Au estimates are [approximately] 1 MT @ [approximately] 1 g/T Au and 0.25 wt. % Cu. Late alteration assemblages may contain a component of magmatic saline fluids generated by observed monzodiorite-granodiorite dikes and pluton emplacement. Massive magnetite ore and associated Na-Ca alteration assemblages were deposited at high temperatures ( 500 to 6000 C), with igneous intrusions providing heat but not necessarily fluids and metals. Later moderate to low temperature Cu-Au mineralization (sulfide + oxide) replaces magnetite, and records the transition to more brittle faulting, with NW �� re-activated NNE structural control, and a greater proportion of magmatic fluids, sulfur ([delta]�����S[subscriptpy] = -1 0/00), and metals. / Graduation date: 2002
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Pre-pliocene structural geology and structural evolution of the northern Los Angeles Basin, southern CaliforniaSchneider, Craig L. 08 March 1994 (has links)
Detailed subsurface structure contour maps and cross sections have shown the
northern Los Angeles basin to be underlain by a south facing monocline that is
complicated by secondary faults and folds. The monocline forms a structural shelf that
marks the northern boundary of the Los Angeles central trough. The monocline and
associated structures are called the Northern Los Angeles shelf. Isopach maps show
that during the Miocene, the predominant structural style was extension. Thick
accumulations of volcanic and volcaniclastic rocks, controlled by normal faults, had a
very different depositional pattern than during the Pliocene. At approximately the
beginning of the Pliocene extension changed to compression resulting in the
reactivation of the Miocene normal faults in a reverse sense and the beginning of the
formation of the monocline and secondary structures. Thick growth sequences were
deposited to the south of the growing monocline toward the present day Los Angeles
central trough.
Fault-bend and fault-propagation fold models are inadmissible solutions to explain
the growth of the monocline. A basement-involved shear model may explain some of
the details of the secondary structures.
Analysis of the Pliocene growth strata shows that the monocline and secondary
structures, the South Salt Lake, the East Beverly Hills, and the Las Cienegas
anticlines, all began to form near the beginning of the Pliocene. All of the secondary
structures became inactive prior to the Upper Pico during the Late Pliocene. Thick
accumulations of Upper Pico growth strata attest to continued monoclinal folding after
the secondary structures became inactive. The growth strata record both the structural
growth and the shortening associated with growth and therefore allow the dip of the
monocline causing fault or shear zone (the Monocline fault) to be calculated. In the
East Beverly Hills area, the growth strata yield a dip of 61°. At Las Cienegas the dip
of the Monocline fault is 62°. These dips are maximum values based on the
assumption the growth strata record all shortening. The fault slip rates for the
Monocline fault are similar in both areas, 1.1-1.2 mm/yr in the East Beverly Hills and
1.3-1.5 mm/yr. in Las Cienegas. The resulting horizontal convergence rates are also
similar, .5-.6 mm/yr and .6-.7 mm/yr respectively.
The Quaternary marine gravels have been deformed into a broad east-west
trending fold, the Wilshire arch. Elastic and non-elastic methods of modeling the
blind fault (Wilshire fault), over which the deformation occurred, yield much greater
shortening rates than for the Pliocene. The non-elastic method involves modeling the
arch as a fault-bend fold. This model predicts a 15° north-dipping thrust with a slip
rate of 1.5-1.9 mm/yr and a horizontal shortening rate of 1.4-1.8 mm/yr. The elastic
method involves matching the observed deformation to that produced on the free
surface by slip on a fault in an elastic half-space. The elastic dislocation model
predicts a right-lateral reverse slip solution with an oblique-slip rate of 2.6-3.3 mm/yr.
This solution yields a horizontal shortening rate of 1.4-1.8 mm/yr. These higher
shortening rates suggest that there was a marked change in tectonic style at the end of
the Pliocene from high-angle faulting and tectonic subsidence to shallow faulting and
uplift. / Graduation date: 1994
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Depositional and tectonic history of the Guerrero Terrane, Sierra Madre de Sur, with emphasis on sedimentary successions of the Teloloapan area, southwestern Mexico /Guerrero-Suastegui, Martin, January 2004 (has links)
Thesis (Ph.D.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 273-299. Also available online.
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Geologic map and structural analysis of the Twin Rocks 7.5 minute quadrangle, Wayne County, Utah /Sorber, Samuel C., January 2006 (has links) (PDF)
Thesis (M.S.)--Brigham Young University. Dept. of Geology, 2006. / Includes bibliographical references.
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Structure of the crust beneath Lake Superior from forward modeling of large aperture seismic dataShay, John T. 30 March 1990 (has links)
Both travel times and amplitudes of large offset refracted and reflected arrivals
observed during GLIMPCE (Great Lakes International Multidisciplinary Program on
Crustal Evolution) along line A in Lake Superior have been modeled using two-dimensional
ray tracing techniques. Forward modeling was used to iteratively refine an
initial velocity model that was constructed from results of tau-sum analysis of the travel
time data at each station combined with information from the coincident common depth
point (CDP) reflection profile. When converted to time the resulting model agrees quite
well with the CDP reflection profile. A 50-100 ms time advance anomaly associated with
the Isle Royal Fault is observed at every station. This anomaly has been modeled as
shallow, high velocity blocks located directly beneath the fault. The blocks correlate well
with the walls of a steep-sided bathymetric trough and are believed to represent highly
indurated upper Keweenawan sediments which may have resulted from hydrothermal
alteration. Approximately 2 km of sedimentary rock (2.8-4.6 km/sec) overlie an 8 km
thick sequence of volcanics and interflow sediments (5.0-6.5 km/sec) within the rift
graben observed on the reflection data. Beneath this sequence is a 6-8 km thick sequence
of 6.6-7.0 km/sec material that is interpreted to represent metamorphosed volcanics. The
velocity of the material at the base of the rift graben is not well constrained
(approximately 7.0 -7.2 km/sec), but probably comprises an additional 10-12 kilometers
of meta-volcanic rocks and intrusions that extend to the base of the graben as imaged on
the CDP reflection profile. Boundaries between these sequences are indicated by
reflections observed at several of the wide-aperture stations. A marked decrease in the
apparent velocity and amplitude of the first arrivals is observed on reversed sections at
ranges exceeding 100 km. This decrease in apparent velocity has been modeled as lower
velocity continental crustal rocks (approximately 6.5 km/sec) at a depth of about 15-20
km adjacent to the 7.0 km/sec material in the graben. Calculation of the gravity response
of the seismic model demonstrates that the gravity high centered over the rift can be
entirely attributed to high density rocks occupying the central half-graben imaged on the
CDP profile. Wide angle reflections from about 15-30 km depth beneath the flanks of the
graben indicate the presence of velocity discontinuities that may represent rift related
detachment surfaces and/or pre-rift structures. Modeling of wide angle reflections
indicate a high degree of structural relief preserved within the lower crust. The high
velocities modeled for this region, coupled with information from the CDP profile,
suggest that the lower crust represents Archean crust that has been either heavily intruded
or underplated by mafic magma. The style and volume of volcanic emplacement is
similar to that of Phanerozoic rifted continental margins and flood basalt provinces. By
analogy, the volcanism within the midcontinent rift appears to have resulted from
decompression melting during lithospheric extension above a broad, asthenospheric
thermal anomaly recently referred to in the literature as the "Keweenawan hot spot". / Graduation date: 1991
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Regional tectonics, sequence stratigraphy and reservoir properties of Eocene clastic sedimentation, Maracaibo Basin, VenezuelaEscalona, Alejandro. January 2003 (has links) (PDF)
Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.
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Géologie et ressources en or du nord-est de la Guinée française ...Goloubinow, Rostislaw. January 1936 (has links)
Thèse--Nancy. / At head of title on added t.p.: Gouvernement général de l'Afrique occidentale française. Service géologique. "Bibliographie": p. 12-16.
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Provenance of Miocene sedimentary sequences in Hengchun Peninsula, Southern Taiwan, and implications for the modern Taiwan orogenYen, Jiun-Yee. Lundberg, Neil. January 2003 (has links)
Thesis (Ph. D.)--Florida State University, 2003. / Advisor: Dr. Neil Lundberg, Florida State University, College of Arts and Sciences, Dept. of Geological Sciences. Title and description from dissertation home page (viewed Mar. 2, 2004). Includes bibliographical references.
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Structural geology and dislocation modeling of the East Coyote anticline, eastern Los Angles basin /Myers, Daniel J. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2002. / Typescript (photocopy). Includes bibliographical references (leaves 42-44). Also available via the World Wide Web.
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Some geomorphological problems related to Hong Kong and the New Territories, with special reference to the coastline /So, Chak-lam. January 1960 (has links)
Thesis (M.A.)--University of Hong Kong, 1961. / Type-written copy. Includes bibliographical references (p. 103-115). Also available on microfilm.
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